src/reader.c

   1 /* Input parser for Bison
   2
   3    Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002, 2003,
   4    2005, 2006, 2007, 2009 Free Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include <quote.h>
  25 #include <quotearg.h>
  26
  27 #include "complain.h"
  28 #include "conflicts.h"
  29 #include "files.h"
  30 #include "getargs.h"
  31 #include "gram.h"
  32 #include "muscle-tab.h"
  33 #include "reader.h"
  34 #include "symlist.h"
  35 #include "symtab.h"
  36 #include "scan-gram.h"
  37 #include "scan-code.h"
  38
  39 static void check_and_convert_grammar (void);
  40
  41 static symbol_list *grammar = NULL;
  42 static bool start_flag = false;
  43 merger_list *merge_functions;
  44
  45 /* Was %union seen?  */
  46 bool union_seen = false;
  47
  48 /* Was a tag seen?  */
  49 bool tag_seen = false;
  50
  51 /* Should rules have a default precedence?  */
  52 bool default_prec = true;
  53 \f
  54 /*-----------------------.
  55 | Set the start symbol.  |
  56 `-----------------------*/
  57
  58 void
  59 grammar_start_symbol_set (symbol *sym, location loc)
  60 {
  61   if (start_flag)
  62     complain_at (loc, _("multiple %s declarations"), "%start");
  63   else
  64     {
  65       start_flag = true;
  66       startsymbol = sym;
  67       startsymbol_location = loc;
  68     }
  69 }
  70
  71 \f
  72
  73 /*------------------------------------------------------------------------.
  74 | Return the merger index for a merging function named NAME.  Records the |
  75 | function, if new, in MERGER_LIST.                                       |
  76 `------------------------------------------------------------------------*/
  77
  78 static int
  79 get_merge_function (uniqstr name)
  80 {
  81   merger_list *syms;
  82   merger_list head;
  83   int n;
  84
  85   if (! glr_parser)
  86     return 0;
  87
  88   head.next = merge_functions;
  89   for (syms = &head, n = 1; syms->next; syms = syms->next, n += 1)
  90     if (UNIQSTR_EQ (name, syms->next->name))
  91       break;
  92   if (syms->next == NULL)
  93     {
  94       syms->next = xmalloc (sizeof syms->next[0]);
  95       syms->next->name = uniqstr_new (name);
  96       /* After all symbol type declarations have been parsed, packgram invokes
  97          record_merge_function_type to set the type.  */
  98       syms->next->type = NULL;
  99       syms->next->next = NULL;
 100       merge_functions = head.next;
 101     }
 102   return n;
 103 }
 104
 105 /*-------------------------------------------------------------------------.
 106 | For the existing merging function with index MERGER, record the result   |
 107 | type as TYPE as required by the lhs of the rule whose %merge declaration |
 108 | is at DECLARATION_LOC.                                                   |
 109 `-------------------------------------------------------------------------*/
 110
 111 static void
 112 record_merge_function_type (int merger, uniqstr type, location declaration_loc)
 113 {
 114   int merger_find;
 115   merger_list *merge_function;
 116
 117   if (merger <= 0)
 118     return;
 119
 120   if (type == NULL)
 121     type = uniqstr_new ("");
 122
 123   merger_find = 1;
 124   for (merge_function = merge_functions;
 125        merge_function != NULL && merger_find != merger;
 126        merge_function = merge_function->next)
 127     merger_find += 1;
 128   aver (merge_function != NULL && merger_find == merger);
 129   if (merge_function->type != NULL && !UNIQSTR_EQ (merge_function->type, type))
 130     {
 131       complain_at (declaration_loc,
 132                    _("result type clash on merge function `%s': <%s> != <%s>"),
 133                    merge_function->name, type, merge_function->type);
 134       complain_at (merge_function->type_declaration_location,
 135                    _("previous declaration"));
 136     }
 137   merge_function->type = uniqstr_new (type);
 138   merge_function->type_declaration_location = declaration_loc;
 139 }
 140
 141 /*--------------------------------------.
 142 | Free all merge-function definitions.  |
 143 `--------------------------------------*/
 144
 145 void
 146 free_merger_functions (void)
 147 {
 148   merger_list *L0 = merge_functions;
 149   while (L0)
 150     {
 151       merger_list *L1 = L0->next;
 152       free (L0);
 153       L0 = L1;
 154     }
 155 }
 156
 157 \f
 158 /*-------------------------------------------------------------------.
 159 | Parse the input grammar into a one symbol_list structure.  Each    |
 160 | rule is represented by a sequence of symbols: the left hand side   |
 161 | followed by the contents of the right hand side, followed by a     |
 162 | null pointer instead of a symbol to terminate the rule.  The next  |
 163 | symbol is the lhs of the following rule.                           |
 164 |                                                                    |
 165 | All actions are copied out, labelled by the rule number they apply |
 166 | to.                                                                |
 167 `-------------------------------------------------------------------*/
 168
 169 /* The (currently) last symbol of GRAMMAR. */
 170 static symbol_list *grammar_end = NULL;
 171
 172 /* Append SYM to the grammar.  */
 173 static symbol_list *
 174 grammar_symbol_append (symbol *sym, location loc)
 175 {
 176   symbol_list *p = symbol_list_sym_new (sym, loc);
 177
 178   if (grammar_end)
 179     grammar_end->next = p;
 180   else
 181     grammar = p;
 182
 183   grammar_end = p;
 184
 185   /* A null SYM stands for an end of rule; it is not an actual
 186      part of it.  */
 187   if (sym)
 188     ++nritems;
 189
 190   return p;
 191 }
 192
 193 static void
 194 assign_named_ref (symbol_list *p, named_ref *named_ref)
 195 {
 196   symbol *sym = p->content.sym;
 197
 198   if (named_ref->id == sym->tag)
 199     {
 200       warn_at (named_ref->loc,
 201                _("duplicated symbol name for %s ignored"),
 202                quote (sym->tag));
 203       named_ref_free (named_ref);
 204     }
 205   else
 206     p->named_ref = named_ref;
 207 }
 208
 209
 210 /* The rule currently being defined, and the previous rule.
 211    CURRENT_RULE points to the first LHS of the current rule, while
 212    PREVIOUS_RULE_END points to the *end* of the previous rule (NULL).  */
 213 static symbol_list *current_rule = NULL;
 214 static symbol_list *previous_rule_end = NULL;
 215
 216
 217 /*----------------------------------------------.
 218 | Create a new rule for LHS in to the GRAMMAR.  |
 219 `----------------------------------------------*/
 220
 221 void
 222 grammar_current_rule_begin (symbol *lhs, location loc,
 223                             named_ref *lhs_named_ref)
 224 {
 225   symbol_list* p;
 226
 227   /* Start a new rule and record its lhs.  */
 228   ++nrules;
 229   previous_rule_end = grammar_end;
 230
 231   p = grammar_symbol_append (lhs, loc);
 232   if (lhs_named_ref)
 233     assign_named_ref(p, lhs_named_ref);
 234
 235   current_rule = grammar_end;
 236
 237   /* Mark the rule's lhs as a nonterminal if not already so.  */
 238   if (lhs->class == unknown_sym)
 239     {
 240       lhs->class = nterm_sym;
 241       lhs->number = nvars;
 242       ++nvars;
 243     }
 244   else if (lhs->class == token_sym)
 245     complain_at (loc, _("rule given for %s, which is a token"), lhs->tag);
 246 }
 247
 248
 249 /*----------------------------------------------------------------------.
 250 | A symbol should be used if either:                                    |
 251 |   1. It has a destructor.                                             |
 252 |   2. --warnings=midrule-values and the symbol is a mid-rule symbol    |
 253 |      (i.e., the generated LHS replacing a mid-rule action) that was   |
 254 |      assigned to or used, as in "exp: { $$ = 1; } { $$ = $1; }".      |
 255 `----------------------------------------------------------------------*/
 256
 257 static bool
 258 symbol_should_be_used (symbol_list const *s)
 259 {
 260   if (symbol_destructor_get (s->content.sym)->code)
 261     return true;
 262   if (warnings_flag & warnings_midrule_values)
 263     return ((s->midrule && s->midrule->action_props.is_value_used)
 264             || (s->midrule_parent_rule
 265                 && symbol_list_n_get (s->midrule_parent_rule,
 266                                       s->midrule_parent_rhs_index)
 267                      ->action_props.is_value_used));
 268   return false;
 269 }
 270
 271 /*----------------------------------------------------------------.
 272 | Check that the rule R is properly defined.  For instance, there |
 273 | should be no type clash on the default action.                  |
 274 `----------------------------------------------------------------*/
 275
 276 static void
 277 grammar_rule_check (const symbol_list *r)
 278 {
 279   /* Type check.
 280
 281      If there is an action, then there is nothing we can do: the user
 282      is allowed to shoot herself in the foot.
 283
 284      Don't worry about the default action if $$ is untyped, since $$'s
 285      value can't be used.  */
 286   if (!r->action_props.code && r->content.sym->type_name)
 287     {
 288       symbol *first_rhs = r->next->content.sym;
 289       /* If $$ is being set in default way, report if any type mismatch.  */
 290       if (first_rhs)
 291         {
 292           char const *lhs_type = r->content.sym->type_name;
 293           const char *rhs_type =
 294             first_rhs->type_name ? first_rhs->type_name : "";
 295           if (!UNIQSTR_EQ (lhs_type, rhs_type))
 296             warn_at (r->location,
 297                      _("type clash on default action: <%s> != <%s>"),
 298                      lhs_type, rhs_type);
 299         }
 300       /* Warn if there is no default for $$ but we need one.  */
 301       else
 302         warn_at (r->location,
 303                  _("empty rule for typed nonterminal, and no action"));
 304     }
 305
 306   /* Check that symbol values that should be used are in fact used.  */
 307   {
 308     symbol_list const *l = r;
 309     int n = 0;
 310     for (; l && l->content.sym; l = l->next, ++n)
 311       if (! (l->action_props.is_value_used
 312              || !symbol_should_be_used (l)
 313              /* The default action, $$ = $1, `uses' both.  */
 314              || (!r->action_props.code && (n == 0 || n == 1))))
 315         {
 316           if (n)
 317             warn_at (r->location, _("unused value: $%d"), n);
 318           else
 319             warn_at (r->location, _("unset value: $$"));
 320         }
 321   }
 322 }
 323
 324
 325 /*-------------------------------------.
 326 | End the currently being grown rule.  |
 327 `-------------------------------------*/
 328
 329 void
 330 grammar_current_rule_end (location loc)
 331 {
 332   /* Put an empty link in the list to mark the end of this rule  */
 333   grammar_symbol_append (NULL, grammar_end->location);
 334   current_rule->location = loc;
 335 }
 336
 337
 338 /*-------------------------------------------------------------------.
 339 | The previous action turns out the be a mid-rule action.  Attach it |
 340 | to the current rule, i.e., create a dummy symbol, attach it this   |
 341 | mid-rule action, and append this dummy nonterminal to the current  |
 342 | rule.                                                              |
 343 `-------------------------------------------------------------------*/
 344
 345 void
 346 grammar_midrule_action (void)
 347 {
 348   /* Since the action was written out with this rule's number, we must
 349      give the new rule this number by inserting the new rule before
 350      it.  */
 351
 352   /* Make a DUMMY nonterminal, whose location is that of the midrule
 353      action.  Create the MIDRULE.  */
 354   location dummy_location = current_rule->action_props.location;
 355   symbol *dummy = dummy_symbol_get (dummy_location);
 356   symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
 357
 358   /* Remember named_ref of previous action. */
 359   named_ref *named_ref = current_rule->action_props.named_ref;
 360
 361   /* Make a new rule, whose body is empty, before the current one, so
 362      that the action just read can belong to it.  */
 363   ++nrules;
 364   ++nritems;
 365   /* Attach its location and actions to that of the DUMMY.  */
 366   midrule->location = dummy_location;
 367   code_props_rule_action_init (&midrule->action_props,
 368                                current_rule->action_props.code,
 369                                current_rule->action_props.location,
 370                                midrule, 0);
 371   code_props_none_init (&current_rule->action_props);
 372
 373   if (previous_rule_end)
 374     previous_rule_end->next = midrule;
 375   else
 376     grammar = midrule;
 377
 378   /* End the dummy's rule.  */
 379   midrule->next = symbol_list_sym_new (NULL, dummy_location);
 380   midrule->next->next = current_rule;
 381
 382   previous_rule_end = midrule->next;
 383
 384   /* Insert the dummy nonterminal replacing the midrule action into
 385      the current rule.  Bind it to its dedicated rule.  */
 386   grammar_current_rule_symbol_append (dummy, dummy_location, named_ref);
 387   grammar_end->midrule = midrule;
 388   midrule->midrule_parent_rule = current_rule;
 389   midrule->midrule_parent_rhs_index = symbol_list_length (current_rule->next);
 390 }
 391
 392 /* Set the precedence symbol of the current rule to PRECSYM. */
 393
 394 void
 395 grammar_current_rule_prec_set (symbol *precsym, location loc)
 396 {
 397   symbol_class_set (precsym, token_sym, loc, false);
 398   if (current_rule->ruleprec)
 399     complain_at (loc, _("only one %s allowed per rule"), "%prec");
 400   current_rule->ruleprec = precsym;
 401 }
 402
 403 /* Attach dynamic precedence DPREC to the current rule. */
 404
 405 void
 406 grammar_current_rule_dprec_set (int dprec, location loc)
 407 {
 408   if (! glr_parser)
 409     warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
 410   if (dprec <= 0)
 411     complain_at (loc, _("%s must be followed by positive number"), "%dprec");
 412   else if (current_rule->dprec != 0)
 413     complain_at (loc, _("only one %s allowed per rule"), "%dprec");
 414   current_rule->dprec = dprec;
 415 }
 416
 417 /* Attach a merge function NAME with argument type TYPE to current
 418    rule. */
 419
 420 void
 421 grammar_current_rule_merge_set (uniqstr name, location loc)
 422 {
 423   if (! glr_parser)
 424     warn_at (loc, _("%s affects only GLR parsers"), "%merge");
 425   if (current_rule->merger != 0)
 426     complain_at (loc, _("only one %s allowed per rule"), "%merge");
 427   current_rule->merger = get_merge_function (name);
 428   current_rule->merger_declaration_location = loc;
 429 }
 430
 431 /* Attach SYM to the current rule.  If needed, move the previous
 432    action as a mid-rule action.  */
 433
 434 void
 435 grammar_current_rule_symbol_append (symbol *sym, location loc,
 436                                     named_ref *named_ref)
 437 {
 438   symbol_list *p;
 439   if (current_rule->action_props.code)
 440     grammar_midrule_action ();
 441   p = grammar_symbol_append (sym, loc);
 442   if (named_ref)
 443     assign_named_ref(p, named_ref);
 444 }
 445
 446 /* Attach an ACTION to the current rule.  */
 447
 448 void
 449 grammar_current_rule_action_append (const char *action, location loc,
 450                                     named_ref *named_ref)
 451 {
 452   if (current_rule->action_props.code)
 453     grammar_midrule_action ();
 454   /* After all symbol declarations have been parsed, packgram invokes
 455      code_props_translate_code.  */
 456   code_props_rule_action_init (&current_rule->action_props, action, loc,
 457                                current_rule, named_ref);
 458 }
 459
 460 \f
 461 /*---------------------------------------------------------------.
 462 | Convert the rules into the representation using RRHS, RLHS and |
 463 | RITEM.                                                         |
 464 `---------------------------------------------------------------*/
 465
 466 static void
 467 packgram (void)
 468 {
 469   unsigned int itemno = 0;
 470   rule_number ruleno = 0;
 471   symbol_list *p = grammar;
 472
 473   ritem = xnmalloc (nritems + 1, sizeof *ritem);
 474
 475   /* This sentinel is used by build_relations in gram.c.  */
 476   *ritem++ = 0;
 477
 478   rules = xnmalloc (nrules, sizeof *rules);
 479
 480   while (p)
 481     {
 482       int rule_length = 0;
 483       symbol *ruleprec = p->ruleprec;
 484       record_merge_function_type (p->merger, p->content.sym->type_name,
 485                                   p->merger_declaration_location);
 486       rules[ruleno].user_number = ruleno;
 487       rules[ruleno].number = ruleno;
 488       rules[ruleno].lhs = p->content.sym;
 489       rules[ruleno].rhs = ritem + itemno;
 490       rules[ruleno].prec = NULL;
 491       rules[ruleno].dprec = p->dprec;
 492       rules[ruleno].merger = p->merger;
 493       rules[ruleno].precsym = NULL;
 494       rules[ruleno].location = p->location;
 495       rules[ruleno].useful = true;
 496       rules[ruleno].action = p->action_props.code;
 497       rules[ruleno].action_location = p->action_props.location;
 498
 499       /* If the midrule's $$ is set or its $n is used, remove the `$' from the
 500          symbol name so that it's a user-defined symbol so that the default
 501          %destructor and %printer apply.  */
 502       if (p->midrule_parent_rule
 503           && (p->action_props.is_value_used
 504               || symbol_list_n_get (p->midrule_parent_rule,
 505                                     p->midrule_parent_rhs_index)
 506                    ->action_props.is_value_used))
 507         p->content.sym->tag += 1;
 508
 509       /* Don't check the generated rule 0.  It has no action, so some rhs
 510          symbols may appear unused, but the parsing algorithm ensures that
 511          %destructor's are invoked appropriately.  */
 512       if (p != grammar)
 513         grammar_rule_check (p);
 514
 515       for (p = p->next; p && p->content.sym; p = p->next)
 516         {
 517           ++rule_length;
 518
 519           /* Don't allow rule_length == INT_MAX, since that might
 520              cause confusion with strtol if INT_MAX == LONG_MAX.  */
 521           if (rule_length == INT_MAX)
 522               fatal_at (rules[ruleno].location, _("rule is too long"));
 523
 524           /* item_number = symbol_number.
 525              But the former needs to contain more: negative rule numbers. */
 526           ritem[itemno++] =
 527             symbol_number_as_item_number (p->content.sym->number);
 528           /* A rule gets by default the precedence and associativity
 529              of its last token.  */
 530           if (p->content.sym->class == token_sym && default_prec)
 531             rules[ruleno].prec = p->content.sym;
 532         }
 533
 534       /* If this rule has a %prec,
 535          the specified symbol's precedence replaces the default.  */
 536       if (ruleprec)
 537         {
 538           rules[ruleno].precsym = ruleprec;
 539           rules[ruleno].prec = ruleprec;
 540         }
 541       /* An item ends by the rule number (negated).  */
 542       ritem[itemno++] = rule_number_as_item_number (ruleno);
 543       aver (itemno < ITEM_NUMBER_MAX);
 544       ++ruleno;
 545       aver (ruleno < RULE_NUMBER_MAX);
 546
 547       if (p)
 548         p = p->next;
 549     }
 550
 551   aver (itemno == nritems);
 552
 553   if (trace_flag & trace_sets)
 554     ritem_print (stderr);
 555 }
 556 \f
 557 /*------------------------------------------------------------------.
 558 | Read in the grammar specification and record it in the format     |
 559 | described in gram.h.  All actions are copied into ACTION_OBSTACK, |
 560 | in each case forming the body of a C function (YYACTION) which    |
 561 | contains a switch statement to decide which action to execute.    |
 562 `------------------------------------------------------------------*/
 563
 564 void
 565 reader (void)
 566 {
 567   /* Initialize the symbol table.  */
 568   symbols_new ();
 569
 570   /* Construct the accept symbol. */
 571   accept = symbol_get ("$accept", empty_location);
 572   accept->class = nterm_sym;
 573   accept->number = nvars++;
 574
 575   /* Construct the error token */
 576   errtoken = symbol_get ("error", empty_location);
 577   errtoken->class = token_sym;
 578   errtoken->number = ntokens++;
 579
 580   /* Construct a token that represents all undefined literal tokens.
 581      It is always token number 2.  */
 582   undeftoken = symbol_get ("$undefined", empty_location);
 583   undeftoken->class = token_sym;
 584   undeftoken->number = ntokens++;
 585
 586   gram_in = xfopen (grammar_file, "r");
 587
 588   gram__flex_debug = trace_flag & trace_scan;
 589   gram_debug = trace_flag & trace_parse;
 590   gram_scanner_initialize ();
 591   gram_parse ();
 592
 593   /* Set front-end %define variable defaults.  */
 594   muscle_percent_define_default ("lr.keep-unreachable-states", "false");
 595   {
 596     char *lr_type;
 597     /* IELR would be a better default, but LALR is historically the
 598        default.  */
 599     muscle_percent_define_default ("lr.type", "LALR");
 600     lr_type = muscle_percent_define_get ("lr.type");
 601     if (0 != strcmp (lr_type, "canonical LR"))
 602       muscle_percent_define_default ("lr.default-reductions", "all");
 603     else
 604       muscle_percent_define_default ("lr.default-reductions", "accepting");
 605     free (lr_type);
 606   }
 607
 608   /* Check front-end %define variables.  */
 609   {
 610     static char const * const values[] = {
 611       "lr.type", "LALR", "IELR", "canonical LR", NULL,
 612       "lr.default-reductions", "all", "consistent", "accepting", NULL,
 613       NULL
 614     };
 615     muscle_percent_define_check_values (values);
 616   }
 617
 618   if (! complaint_issued)
 619     check_and_convert_grammar ();
 620
 621   xfclose (gram_in);
 622 }
 623
 624
 625 /*-------------------------------------------------------------.
 626 | Check the grammar that has just been read, and convert it to |
 627 | internal form.                                               |
 628 `-------------------------------------------------------------*/
 629
 630 static void
 631 check_and_convert_grammar (void)
 632 {
 633   /* Grammar has been read.  Do some checking.  */
 634   if (nrules == 0)
 635     fatal (_("no rules in the input grammar"));
 636
 637   /* Report any undefined symbols and consider them nonterminals.  */
 638   symbols_check_defined ();
 639
 640   /* If the user did not define her ENDTOKEN, do it now. */
 641   if (!endtoken)
 642     {
 643       endtoken = symbol_get ("$end", empty_location);
 644       endtoken->class = token_sym;
 645       endtoken->number = 0;
 646       /* Value specified by POSIX.  */
 647       endtoken->user_token_number = 0;
 648     }
 649
 650   /* Find the start symbol if no %start.  */
 651   if (!start_flag)
 652     {
 653       symbol_list *node;
 654       for (node = grammar;
 655            node != NULL && symbol_is_dummy (node->content.sym);
 656            node = node->next)
 657         {
 658           for (node = node->next;
 659                node != NULL && node->content.sym != NULL;
 660                node = node->next)
 661             ;
 662         }
 663       aver (node != NULL);
 664       grammar_start_symbol_set (node->content.sym,
 665                                 node->content.sym->location);
 666     }
 667
 668   /* Insert the initial rule, whose line is that of the first rule
 669      (not that of the start symbol):
 670
 671      accept: %start EOF.  */
 672   {
 673     symbol_list *p = symbol_list_sym_new (accept, empty_location);
 674     p->location = grammar->location;
 675     p->next = symbol_list_sym_new (startsymbol, empty_location);
 676     p->next->next = symbol_list_sym_new (endtoken, empty_location);
 677     p->next->next->next = symbol_list_sym_new (NULL, empty_location);
 678     p->next->next->next->next = grammar;
 679     nrules += 1;
 680     nritems += 3;
 681     grammar = p;
 682   }
 683
 684   aver (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
 685
 686   /* Assign the symbols their symbol numbers.  Write #defines for the
 687      token symbols into FDEFINES if requested.  */
 688   symbols_pack ();
 689
 690   /* Scan rule actions after invoking symbol_check_alias_consistency (in
 691      symbols_pack above) so that token types are set correctly before the rule
 692      action type checking.
 693
 694      Before invoking grammar_rule_check (in packgram below) on any rule, make
 695      sure all actions have already been scanned in order to set `used' flags.
 696      Otherwise, checking that a midrule's $$ should be set will not always work
 697      properly because the check must forward-reference the midrule's parent
 698      rule.  For the same reason, all the `used' flags must be set before
 699      checking whether to remove `$' from any midrule symbol name (also in
 700      packgram).  */
 701   {
 702     symbol_list *sym;
 703     for (sym = grammar; sym; sym = sym->next)
 704       code_props_translate_code (&sym->action_props);
 705   }
 706
 707   /* Convert the grammar into the format described in gram.h.  */
 708   packgram ();
 709
 710   /* The grammar as a symbol_list is no longer needed. */
 711   symbol_list_free (grammar);
 712 }